Printer cartridges and memory devices containing compressed multi-dimensional color tables

ABSTRACT

In one example in accordance with the present disclosure a printer cartridge and memory device containing a representation of a compressed multi-dimensional color table is described. The color table includes at least one low dimensional portion of the multi-dimensional color table storing color transformation information at a first resolution and a number of remaining portions of the multi-dimensional color table storing color transformation information at a second resolution. In the color table, the first resolution is greater than the second resolution and the at least one compressed multi-dimensional color table is to generate a high resolution uncompressed multi-dimensional color table the high resolution being at least as great as the first resolution.

BACKGROUND

Many output devices such as ink printers and laser printers implement asubtractive color model while input devices such as computer monitors,mobile phones, and other input devices implement an additive colormodel. For example, output devices may use a CMYK (cyan, magenta, yellowand black) color model, while input devices may use a RGB (red, greenand blue) color model. To output data from an input device such as agraphic, text or a combination thereof, output devices convert theadditive color model into a subtractive color model.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various examples of the principlesdescribed herein and are a part of the specification. The illustratedexamples do not limit the scope of the claims.

FIG. 1 is a diagram of input devices, an output device, and a printercartridge containing compressed multi-dimensional color tables,according to one example of the principles described herein.

FIG. 2 is a diagram of a printer cartridge with a memory devicecontaining a compressed multi-dimensional color table, according to oneexample of the principles described herein.

FIG. 3 is a diagram of a memory device with a compressedmulti-dimensional color table, according to one example of theprinciples described herein.

FIG. 4 is a diagram of a compressed multi-dimensional color table,according to one example of the principles described herein.

FIG. 5 is a diagram of a plane of a compressed multi-dimensional colortable, according to one example of the principles described herein.

FIG. 6 is a diagram of a plane of a compressed multi-dimensional colortable including interpolated nodes, according to one example of theprinciples described herein.

FIG. 7 is a diagram of a printer cartridge with a memory devicecontaining a pointer to a compressed multi-dimensional color table,according to one example of the principles described herein.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION

Input devices may implement one color model, such as an additive colormodel to visually display text or images. For example, an input devicemay implement an RGB color model. An input device may implement varioustypes of RGB color models. Examples of RGB color models include sRGB,Adobe® RGB and scan RGB. As used herein, the various types of RGB colormodels may be referred to generically as an RGB color model, or similarterminology.

Before an input image can be printed as a physical output, the inputcolor model (RGB, for example) is converted to an output color model(CMYK, for example). This may be done using a color transformation tablethat includes color transformation information used by a processor toconvert input color data, such as RGB color data into output color data,such as CMYK color data.

However, current color transformation processes may produceunsatisfactory results. For example, the content of the colortransformation from one model to another model is highly dependent onthe output media formulation. Still further, the color transformationmay be dependent on fluid properties of the ink, the ink's reflectiveproperties when printed on various substrates, and other inherentproperties of the ink or toner. Similar principles may apply to othercolorants such as toner. As a result, different cartridges, anddifferent ink types may output different representations of input color.

Moreover, uncompressed color tables occupy a lot of space on a memorydevice, which is exacerbated when the color table is to be stored on aprinter cartridge, where space is at a premium. This effect is furthercompounded as an output device may rely on a number of color transformtables which can be large and take up valuable memory space.Accordingly, reducing the space on a memory device occupied by a colortable reduces the size of the memory device or frees up space on thememory device for other storage needs.

Accordingly, the present disclosure describes a memory device thatincludes a compressed multi-dimensional color table. The memory devicemay be for use with, or disposed on a printer cartridge. For example,the memory device contains a number of compressed multi-dimensionalcolor tables. A compressed multi-dimensional color table includes lowdimensional portions that contain color transformation informationstored at a higher resolution. Remaining portions of the compressedmulti-dimensional color table, such as higher dimensionalrepresentations contain color transformation information stored at alower resolution, relative to the higher resolution.

A compressed multi-dimensional color table that encodes low dimensionaldata at higher resolutions and remaining data at lower resolutionsprovides compact storage of color transformation information whilemaintaining a higher resolution for certain portions of a color table.Moreover, the compressed color table stored on the memory device willenable for perceptually lossless compression of color tables atsignificant compression rates. Accordingly, the compressed color tableallows for lossless compression results while meeting the storageallocation of a memory device of a printer cartridge. The portions ofthe multi-dimensional color table that are stored at higher resolutionsmay reflect an intended use of the color table. For example, thecompressed multi-dimensional color table may preserve portions of thecolor table that correspond to colors that are most susceptible to errorperception by the human eye, thus increasing the overall quality of thecompressed color table. More specifically, portions of a color tablethat are near the neutral axis (i.e., a line between black and white ina color table), that may be referred to as shades of gray, skin-toned orearth-toned colors may be desired to be stored at a higher resolution.In this example, a compressed multi-dimensional color table allows formore accuracy in these neutral, gray, skin-toned, or earth-tonedportions, and greater compression in interpolated or predicted datapoints where increased resolution may not be needed all whilemaintaining a lossless overall transformation. In another example, forexample the printing of a corporate logo, greater compression may bedesirable in the neutral, gray, skin-toned, or earth-toned portionswhile maintaining greater resolution for colors used in the corporatelogo. In yet another example, more accuracy may be desired in corporatelogo colors in addition to the neutral colors. In other words, thepresent disclosure describes a data structure that compresses eachcolorant more efficiently.

Still further, including the color transformation information on amemory device of the printer cartridge allows for printer cartridgespecific information to be stored, rather than generic colortransformation information that is stored on a printer or a printerdriver. For example, a compressed multi-dimensional color table storedon a memory device of a printer cartridge, removes the color tables froma printer or other electronic device. The color table is optimized forthe inks in the cartridge. For example, updates and adjustments to thecolor tables would not include pushing table updates via a printerprogram instruction or a printer driver update. Additionally, a memorydevice that comprises a representation of the compressed color table,such as the color table or a pointer, affords greater flexibility andcustomization in the selection and use of various printer cartridges.

Still further, compressing the color table may reduce the amount ofmemory used to store information. For example, an uncompressed 17-cubedRGB-indexed CMYK-output color table uses 19,562 bytes of storage. Bycomparison a compressed multi-dimensional color table described herein,with a higher resolution portion such as the neutral axis that has 17nodes along its length and the rest of the color table having 5 nodesalong the axes uses less bytes of storage. Removing the redundant nodes,the compressed multi-dimensional table with higher resolution lowdimensional portions and lower resolution high dimensional portions uses548 bytes. These 548 bytes are accounted for as follows: 17 bytescorresponding to the nodes along the neutral axis plus 5³ bytes less 5bytes of the redundant nodes, the 5³ less 5 corresponding to theremaining portions. While the application makes references to 5-noderesolution and 17-node resolution, any level of resolution may be usedin accordance with the present specification, including 3-noderesolution, 33-node resolution, and even up to 256-node resolution.

For example, the present specification describes a printer cartridgethat includes a memory device and at least one compressedmulti-dimensional color table stored on the memory device. Thecompressed multi-dimensional color table includes at least one lowdimensional portion of the multi-dimensional color table storing colortransformation information at a first resolution and a number ofremaining portions of the multi-dimensional color table storing colortransformation information at a second resolution; the first resolutionbeing greater than the second resolution. The multi-dimensional colortable is to generate a high resolution uncompressed multi-dimensionalcolor table, the high resolution being at least as great as the firstresolution.

The present specification also describes a memory device that includesat least one compressed multi-dimensional color table. The compressedmulti-dimensional color table includes a first number of nodes along alow dimensional portion of the multi-dimensional color table storingcolor transformation information at a first resolution and a secondnumber of nodes along a number of remaining portions of themulti-dimensional color table storing color transformation informationat a second resolution; the first resolution being greater than thesecond resolution. The multi-dimensional color table is to generate ahigh resolution uncompressed multi-dimensional color table, the highresolution being at least as great as the first resolution.

The present specification also describes a memory device that includes arepresentation of at least one compressed multi-dimensional color table.The compressed multi-dimensional color table includes a first number ofnodes along a low dimensional portion of the multi-dimensional colortable. The first number of nodes store color transformation informationat a first resolution. The compressed multi-dimensional color table alsoincludes a second number of nodes along a number of remaining portionsof the multi-dimensional color table. The second number of nodes storecolor transformation information at a second resolution; the firstresolution being greater than the second resolution. Themulti-dimensional color table is to generate a high resolutionuncompressed multi-dimensional color table, the high resolution being atleast as great as the first resolution.

As used in the present specification and in the appended claims, theterm “multi-dimensional color table” or similar language refers broadlyto a color table that includes color transformation information atvarious dimensions. For example, a color table may be three-dimensionaland visualized as a cube with each axis pertaining to an input colorvalue. In one example, an RGB color transform cube may include nodesthat are indexed by R, G, and B values, with each R, G, B colorcomponent representing an input dimension in the 3-dimensional RGB colortransform. The multi-dimensional color table may be sub-divided into anumber of smaller dimensional representations.

Still further, as used in the present specification and in the appendedclaims a “low dimensional” or “lower dimensional” portion or similarlanguage refers broadly to a portion of the multi-dimensional colortable that is less than the full dimension of the color table. Forexample, given a three-dimensional color table, a lower dimension, orlower dimensional portion may refer to a planar section of the cube,i.e., a 2D portion, or a linear section of the cube connecting twopoints within the cube, i.e., a 1D portion. Still further, a “remainingportion” or similar language refers broadly to a portion of themulti-dimensional color table that is not identified aslower-dimensional or intermediate dimensional.

Still further, as used in the present specification and in the appendedclaims, “neutral color” may refer to those colors that are near theneutral axis. Examples of neutral colors include shades of gray,earth-toned colors, and skin-toned colors.

Still further, as used in the present specification and in the appendedclaims, “color difference” may refer to the difference in color valuesof adjacent nodes in an uncompressed color table. For examples,node-pairs along the neutral axis, or node-pairs near the neutral axissuch as skin-toned colors, may have smaller color value differencesrelative to node-pairs that are farther away from the neutral axis.

Still further, in the present specification and in the appended claims,the term “lossless compression,” or similar language, refers broadly tocompression wherein the original data, is reconstructed from thecompressed data, such that the differences between the original data andthe compressed data are imperceptible. In one example, “digitallylossless compression” includes compression where there is no digitaldifference between the original data and the compressed data and“perceptually lossless compression” includes compression where there aredigital differences between the original data and the compressed data,but the differences are not visible to the consumer of the data. The lowdimensional portions may be digitally losslessly compressed.

Yet further still, in the present specification and in the appendedclaims, the term “interpolated color table” or similar terminology mayinclude a color table that comprises 1) a number of actual nodes thatcorrespond to nodes from a base color table such as themulti-dimensional color table and 2) a number of interpolated nodes thatare interpolated from a base color table using any mathematicalinterpolation method. The interpolated nodes may include interpolatednode values.

Still further, in the present specification and in the appended claims,the term “neutral axis” may include a line extending from the origin ofa three-dimensional color table to the node of the color table farthestfrom the origin. One of the origin node and the farthest nodecorresponds to the color white, and the other corresponds to the colorblack. Colors along the neutral axis may be referred to as “neutralcolors,” “near-neutral colors,” or similar terminology and may be thosecolors where small differences or errors are most accurately discernedby the human eye. Accordingly, deviations along the neutral axis aremore easily perceived by the human eye.

Lastly, as used in the present specification and in the appended claims,the term “a number of” or similar language may include any positivenumber comprising 1 to infinity; zero not being a number, but theabsence of a number.

In the following description, for purposes of explanation, numerousdetails are set forth in order to provide a thorough understanding ofthe present systems and methods. It will be apparent, however, to oneskilled in the art that the present apparatus, systems, and methods maybe practiced without these details. Reference in the specification to“an example” or similar language means that a particular feature,structure, or characteristic described is included in at least that oneexample, but not necessarily in other examples.

FIG. 1 is a diagram of input devices (101-1, 101-2, 101-3, 101-4), anoutput device (102), and a printer cartridge (103) having a compressedmulti-dimensional color table (105), according to one example of theprinciples described herein. In some examples, via an input device (101)a user may generate data to be output in tangible form. The data may betext, an image, or combinations thereof. In one example of generatinginput to be physically output, a user uses a word processing computerprogram on a computer (101-1), laptop (101-2), smart phone (101-3),personal digital assistant (101-4) or other input device (101) togenerate a text document. In another example, a user generates, orotherwise obtains a graphic. Examples of input devices (101) include,computers, laptops, digital cameras, mobile devices, personal digitalassistants (PDAs), tablets, and other input devices. An output device(102) may be used to output a physical version of the generated data.For example, a printer may print the text document or the graphic ontopaper. Examples of output devices (102) include laser printers and inkprinters.

A printer cartridge (103) may be used with an output device (102) togenerate a physical output based on information received from an inputdevice (101). For example, the printer cartridge (103) may be an inkcartridge that contains liquid ink for use with an inkjet printer. Inanother example, the printer cartridge (103) may be a toner cartridgethat contains dry toner powder for use with a laser printer. In oneexample, the printer cartridge (103) is a three-dimensional printercartridge (103) such that the printer cartridge (103) can be used forthree-dimensional printing. As will be described below, the printercartridge (103) may comprise a number of compressed color tables, orrepresentations of a number of compressed color tables that convert aninput device (101) color model to an output device (102) color model.

The printer cartridge (103) includes a compressed multi-dimensionalcolor table (105). The multi-dimensional color table (105) includesportions that are stored at a higher resolution and portions that arestored at a lower resolution. The multi-dimensional color table (105)may be compressed as some of the information is stored at a lowerresolution, and therefore smaller size. In other words, if all theentries of the multi-dimensional color table (105) were stored at ahigher resolution, then the multi-dimensional color table (105) wouldnot be a compressed color table.

In some examples, a number of printer cartridges (103) may be used withan output device (102) to generate an output. For example, when usedwith an inkjet printer, multiple printer cartridges (103) may be used.More specifically, one printer cartridge (103) may include black ink andanother printer cartridge (103) may include cyan, magenta and yellowink. In another example, one printer cartridge (103) may include blackink, another printer cartridge (103) may include cyan ink, anotherprinter cartridge (103) may include magenta ink, and another printercartridge (103) may include yellow ink. Accordingly, each printercartridge (103) may contain a number of compressed color tablescorresponding to the ink colors included in the printer cartridge (103).While FIG. 1 depicts a number of input devices (101), and an outputdevice (102), in one example, the present specification is directed to aprinter cartridge (103) and memory device containing a compressed colortable.

FIG. 2 is a diagram of a printer cartridge (103) with a memory device(204) containing a compressed multi-dimensional color table (105),according to one example of the principles described herein. The memorydevice (204) stores data relating to the conversion of input data tooutput data. For example, the memory device (204) may store a number ofcompressed multi-dimensional color tables (105) that convert an inputcolor model into an output color model. The memory device (204) may beimplemented with other electronic components to generate a physicaloutput. For example, the memory device (204) may be coupled to a printercartridge controller (not shown) that controls the distribution of anoutput media (e.g., ink or toner) onto a physical substrate. In someexamples, a memory device (204) is disposed on the printer cartridge(103). In other examples, the memory device (204) is independent of theprinter cartridge (103) and programmed to be used with the printercartridge (103).

As described above, the memory device (204) stores a representation ofcompressed multi-dimensional color tables (105) that transform receiveddata from an input color model to an output color model. For example,FIG. 2 depicts an example where the representation is the compressedmulti-dimensional color table (105) which is stored on the memory device(204) and FIG. 7 depicts an example where the representation is apointer to the compressed multi-dimensional color table (105). Acompressed multi-dimensional color table (105) specifies thetransformations of an input model (such as sRGB, adobe RGB, scan RGB,for example) to an output model. For simplicity, the presentspecification discusses the color transformation with regards to athree-dimensional RGB color model, however the compressedmulti-dimensional color tables (105) may convert any number, and anytype, of input color models into any number, and any type, of outputcolor models. For example, the multi-dimensional color table may be afour-dimensional CMYK table. Examples of color models that may beconverted include, a Specifications for Web Offset Publications (SWOP)CMYK model and the International Commission on Illumination (CIE) L*a*b*color model.

Each compressed multi-dimensional color table (105) includes at leastone low dimensional portion that stores color transformation informationat a first resolution and a number of remaining portions that storecolor transformation information at a second resolution, in which thefirst resolution is greater than the second resolution. For example; lowdimension transitions; such as the neutral axis; or otherone-dimensional axes within the three-dimensional color table may bestored at a higher resolution (i.e., 17 node resolution) than the restof the of the three-dimensional color table (105), which for example maybe stored at a 5-node resolution. The low dimensional portions may bestored at a higher resolution to preserve the accuracy of the colortransformation information thereby increasing the accuracy of theseregions.

In some examples; the low dimensional portion, the remaining portions,or combinations thereof may be used by multiple applications. In otherwords, the low dimensional portion of the multi-dimensional color table(105) may be the same as at least one low dimensional portion of anothermulti-dimensional color table of another printer cartridge. For example,a single low dimensional higher resolution neutral axis may be storedand used in the creation of several color look-up tables (CLUTs)relative to various paper types and various print qualities. Sharingsuch information for multiple paper types and multiple paper qualitiesfurther reduces the use of memory on a printer cartridge (103).

Storing the compressed multi-dimensional color table (105) or a pointeron a memory device (204) either used with, or disposed on, a printercartridge (103) allows greater flexibility in output mediacustomization. For example, updates to the color transformation can bedistributed via the printer cartridges (103) as opposed to pushingprinter program instructions or printer driver updates. Additionally, asthe color transformation is heavily dependent on the ink or tonerformulation, a more accurate representation of the input color model maybe generated when the compressed multi-dimensional color table (105) istailored to a specific printer cartridge (103) rather than stored on anoutput device (FIG. 1, 102) that may implement various kinds of printercartridges (103). Additionally, compressed color tables (105) may beupdated as ink or toner formulation changes.

Moreover, including higher resolution low dimensional portions and lowerresolution remaining portions of the color table (105) allows forimproved memory usage while preserving the quality of certain portionsof the color transformation table.

FIG. 3 is a diagram of a memory device (204) with a compressedmulti-dimensional color table (105), according to one example of theprinciples described herein. As described above, in some examples, thecompressed multi-dimensional color table (105) may be represented as athree-dimensional cube; each axis of the cube corresponds to a color ofthe input color model. For example, in an RGB-indexed color table (105),the x-axis (306) may correspond to the color green, the y-axis (307) maycorrespond to the color red, and the z-axis (308) may correspond to thecolor blue. A number of lines divide each plane of the cube as indicatedin FIG. 3 by the dashed lines (311). For simplicity, in FIG. 3 a singleline (311) has been indicated by a reference numeral. The intersectionof two lines is designated as a node (309) that indicates atransformation from the input colorant indicated by the index of thenode (309) in the cube, to an output colorant indicated by a node value.More specifically, each node (309) is indexed by the input color modelcolorants (e.g., R, G, B as depicted in FIG. 3) and a node valueindicates the output colorant combination that generates an outputcolorant corresponding to the input colorant for that node (309).

The accuracy of the color transformation depends on the number of nodes(309). In some examples, the accuracy of the color transformation isreferred to as the resolution of the color table. For example, a 5-cubedcolor table generates a less accurate output representation of the inputcolor model. This may be referred to as a lower-resolution color table.By comparison, a 17-cubed color table generates a more accurate outputrepresentation of the input color mode. This may be referred to as ahigher resolution color table.

As will be described in FIG. 4, the compressed multi-dimensional colortable (105) is sub-divided into dimensional portions, each dimensionalportion containing a number of nodes (309). The number of nodes in agiven dimensional portion defines a resolution of that portion. Forexample, the compressed multi-dimensional color table (105) includesnodes (309) along a low dimensional portion, which nodes (309) storecolor transformation information at a first resolution. Themulti-dimensional color table (105) also includes nodes (309) alongother portions, which nodes (309) store color transformation informationat a second, and lower, resolution. As described above, those nodes ofother portions, which are not along the low dimensional portion, may bereferred to as nodes of a remaining portions. In other words, thecompressed multi-dimensional color table (105) may include portions thatare at a lower resolution relative to other portions. In a specificnumeric example, the compressed multi-dimensional color table (105)includes a one-dimensional portion, such as the neutral axis or otherlower dimensional transition that contains 17 points along its lengthand contains other portions, such as a number of two-dimensional slicesof the three-dimensional cube that include 5 nodes along its axes.

In some examples, the resolution of portions of the compressedmulti-dimensional color table (105) may be selected based on intendedapplication. For example, differences in vivid colors are less easilyperceived by the human eye. Accordingly, nodes (309) corresponding tothese vivid colors may have a lower resolution. By comparison,differences in “near-neutral” colors (i.e., colors close to a neutralaxis of the cube such as earth-toned colors, skin-toned colors, orshades of gray) may be more easily perceived. Accordingly, nodes (309)corresponding to these near-neutral colors may have a higher resolution.

In another example, the portions of the multi-dimensional color table(105) that are stored at a higher resolution may be those colors havinglarger color differences between node-pairs relative to the remainingportions as measured by a color difference metric. Such metrics includethe International Commission on Illumination (CIE) Delta E metric, CIE76formula, CIE94 formula, CIEDE2000, and CMC I:c metric. For example, in acorporate logo, it may be desirable to have greater resolution for acolor heavily used in the corporate logo, for example, green, whereas itmay not be as relevant to have great resolution for earth-toned colorssuch as brown or beige as such colors may not be present in thecorporate logo. In other words, the compressed multi-dimensional colortable (105) may include any number of different portions of the table(105) stored at a higher resolution, depending upon, for example, theapplication.

The compressed multi-dimensional color table (105) may correspond to aparticular media type. For example, particular paper types, orparticular paper colors may have corresponding compressedmulti-dimensional color tables (105). For example, one compressedmulti-dimensional color table (105) may correspond to plain paper andanother compressed multi-dimensional color table (105) may correspond tothicker paper, such as company letterhead, or bond paper. In anotherexample, different degrees of output quality may have differentcompressed multi-dimensional color tables (105). For example, a “draft”quality may have one compressed multi-dimensional color table (105), anda “best” quality may have a different compressed multi-dimensional colortable (105). In yet another example, different input devices (FIG. 1,101) may have different corresponding compressed multi-dimensional colortables (105). For example, a mobile device may have one correspondingcompressed multi-dimensional color table (105), and a digital camera mayhave a different corresponding compressed multi-dimensional color table(105).

FIG. 4 is another diagram of a compressed multi-dimensional color table(105), according to one example of the principles described herein. Asdescribed above, a color table may be represented by a three-dimensionalcube having a number of nodes (FIG. 3, 309). The compressedmulti-dimensional color table (105) may be broken up into a number ofdimensional representations. For example, a three-dimensional compressedcolor table (105) may include a number of low dimensional portions. Aspecific example is a one-dimensional portion (412) of thethree-dimensional compressed color table (105). A one-dimensionalportion (412) of a compressed multi-dimensional color table (105) mayrefer to a line connecting two nodes (FIG. 3, 309); all nodes (FIG. 3,309) along that line being a part of the one-dimensional portion (412).For example, as depicted in FIG. 4, a one-dimensional portion (412) maybe a line connecting nodes (FIG. 3, 309) at the lower left hand cornerof a front face to the upper right hand corner of the front face. WhileFIG. 4 specifically depicts one example of a one-dimensional portion(412) the compressed multi-dimensional color table (105) may be made upof a number of one-dimensional portions that connect different pointswithin the color space.

Similarly, a three-dimensional compressed color table (105) may includea number of remaining portions, a remaining portion being a portion thatincludes nodes not identified as pertaining to the low dimensionportion. For example, if a one dimension portion is identified as a lowdimension portion, a two-dimensional portion (413) of thethree-dimensional compressed color table (105) may be included as aremaining portion. A two-dimensional portion (413) may be a planarslice, face, or other portion defined by two axes of the compressedmulti-dimensional color table (105). While reference in FIG. 4 is madeto a three-dimension compressed color table (105), a one-dimensionalportion (412), and a two-dimensional portion (413), a compressedmulti-dimensional color table (105) may include any number ofdimensions. For example, the compressed multi-dimensional color table(215) may be a four-dimensional table, such as a table representing aCMYK input color model.

In summary, each compressed multi-dimensional color table (105) isdivisible into a number of other dimensions. A low dimension being adimension less than the full-dimension of the compressed color table(105). For example, in a three-dimensional representation of a colortable, when a low dimensional portion may be a one-dimensional portionor a two-dimensional portion, the remaining portion being that portionnot defined as a low dimensional portion.

A resolution of a portion of a color table (105) is defined by thenumber of nodes (309) along a particular axis. For example, aone-dimensional portion with five nodes along its length may be lowerresolution than a one-dimensional portion with seventeen nodes along itslength. Similarly, a two-dimensional portion with five nodes along itsaxes may be lower resolution than a two-dimensional portion withseventeen nodes along its axes. The accuracy of the color transformationdepends on the number of nodes of the color table. In some examples, theaccuracy of the color transformation may be referred to as theresolution of the color table. For example, a 5-cubed color tablegenerates a less accurate output representation of the input colormodel. This may also be referred to as a low-resolution color table. Bycomparison, a 17-cubed color table generates a more accurate outputrepresentation of the input color mode. This may be referred to as ahigh-resolution color table.

While FIG. 4 indicates two different resolutions, any number ofresolutions may be used in the compressed color table (105). Forexample, the compressed color table may include a third number of nodesalong an intermediate portion of the compressed multi-dimensional colortable that store color transformation at a third resolution, which thirdresolution is the same as or different from the second resolution andfirst resolution. In other words, the compressed multi-dimensional colortable (105) may include any number of portions of nodes that containcolor transformation information encoded to any number of differentresolution levels. In this example, the high resolution uncompressedcolor table may be a resolution that is at least as great as the highestof the first resolution and the third resolution.

FIG. 5 is a diagram of a plane of a compressed multi-dimensional colortable (105), according to one example of the principles describedherein. For example, FIG. 5 depicts a number of dimensional portions ofthe compressed multi-dimensional color table (105) at differentresolutions. As described above, the compressed multi-dimensional colortable (FIG. 1, 105) may include a low dimensional portion that storescolor transformation information at a first resolution. For example, asdepicted in FIG. 5, the one-dimensional portion (412) of the compressedmulti-dimensional color table (105) may have a higher resolution thanthe two-dimensional portion (413) as indicated by the greater number ofnodes (309-1) along the one-dimensional portion (412) as compared to thenumber of nodes (309-2) along the axes of the two-dimensional portion(413). In a specific numeric example, the one-dimensional portion (412)may have 17 nodes along its length as compared to a two-dimensionalplane (413) that may have 5 nodes along its axes. A number of redundantnodes (309-3), that are both part of a one-dimensional portion (412) anda two-dimensional portion (413), are accounted for accounted for onetime when determining the total bytes used by a compressedmulti-dimensional color table (105).

The compressed multi-dimensional color table (FIG. 1, 105) may have morethan one low dimensional portion that is stored at a higher resolution.For example, a neutral axis may have more nodes along its lengthrelative to remaining portions (e.g., two- or three-dimensionalportions). At the same time other axes, such as the axis between blackand green, black and red, and black and blue among other axes may alsostore color transformation at the first resolution, having more nodes(309) along their lengths than other, higher dimensional, portions ofthe compressed multi-dimensional color table (105). Other examples oflow dimensional portions that may be stored at higher resolution includetransitions from primary colors to secondary colors.

As described above, encoding a compressed multi-dimensional color table(105) to include portions at different resolutions increases memoryefficiency by reducing the size of a color table while maintaining thoseportions that benefit from a more accurate color transformation.

FIG. 6 is a diagram of a plane of a compressed multi-dimensional colortable (105) including interpolated nodes (309-5), according to oneexample of the principles described herein. The compressedmulti-dimensional color table (105) may be used to generate a highresolution uncompressed multi-dimensional color table, the highresolution being at least as great as the highest resolution in thecompressed multi-dimensional table (FIG. 1, 105). For example, the lowdimensional higher resolution portion (i.e., one-dimensional portion(412)) and the remaining dimensional lower resolution portion (of whichthe two-dimensional portion (413) may be an example) can, using any formof interpolation, be used to interpolate higher resolution colortransformation information. For simplicity, in FIG. 6, all nodes (309-4)that fall along the remaining portion and the low resolution portionthat are not interpolated nodes (309-5) are indicated with a solid-linecircle. In other words the non-interpolated nodes (309-4) include theredundant nodes (FIG. 3, 309-3), nodes (FIG. 3, 309-1) that fall alongthe high resolution portion and nodes (FIG. 3, 309-2) that fall alongthe lower resolution portion. Nodes (FIG. 3, 309-1) that fall along thehigher resolution remaining portions are indicated in FIG. 6 as circleshaving a solid outline and cross-hatched fill. By comparison, theinterpolated nodes (309-5), indicated by the dashed circles, may be nodevalues that are interpolated from the non-interpolated nodes (309-4) orother interpolated nodes (309-5). For simplicity a single instance of anon-interpolated node (309-4) and an interpolated node (309-5) areindicated by reference numbers.

Using any interpolation method, the non-interpolated nodes (309-4),i.e., the nodes (FIG. 5, 309-1, 309-2, 309-3) of the higher and lowerresolution portions respectively, a high resolution uncompressedmulti-dimensional color table is generated.

The multi-dimensional color table (FIG. 1, 105) may include a number ofnode addresses to individually address nodes within the compressedmulti-dimensional color tale (FIG. 1, 105). In some examples, theinterpolation and generation of the uncompressed multi-dimensional colortable is generated prior to a request. For example, it may be apre-request process that occurs as the printer cartridge (FIG. 1, 103)is loaded into an output device (FIG. 1, 102). In this example, viasimple linear interpolation, interpolated nodes (309-5) are calculatedusing adjacent non-interpolated nodes (309-4) or other adjacentinterpolated nodes (309-5). Accordingly, a full uncompressed color tablemay be generated prior to any request for an output. Subsequent requestsmay then rely on the full uncompressed color table.

In some examples, the generation of the high resolution colortransformation information may be in response to request to generate anoutput. In other words, the generation of uncompressed colortransformation information may be performed in real time. In thisexample, rather than uncompressing the entire uncompressed color table,just those portions indicated in the request are decompressed. As eachof the nodes are individually addressable, less than all of the nodesmay be relied on, the nodes relied on being identified based on theinformation received in a request.

Using both the higher resolution data and the lower resolution dataallows a more accurate color transformation based on the use of thehigher resolution data near the lower dimensional portion of thecompressed multi-dimensional color table (105). For example, as depictedin FIG. 5, a one-dimensional portion (412) may be a losslesslycompressed portion as color changes along this portion are intended tobe stored at a higher resolution based on the application. In otherwords, the one-dimensional portion (412) may include more nodes (309-4),indicated by the solid cross-hatched circles, than a two-dimensionalportion (413), nodes (309-4) in the two-dimensional portion (413) areindicated by the solid unfilled circles.

Similarly, distinctions in nodes close to the one-dimensional portion(412) are also intended to have a high resolution. For example, theinterpolated nodes (309-5) that are closer to the higher resolutionone-dimensional nodes (309-4, hatched) are influenced by those higherresolution one-dimensional nodes (309-4, hatched) and thus theiraccuracy is improved due to the effect of interpolation from anon-interpolated node (309-4) as opposed to interpolation from aninterpolated node (309-5). The interpolated nodes (309-5) that areinfluenced by the higher resolution one-dimensional nodes (309-4,hatched) are indicated as dashed circles having a vertical hatching. Ascan be seen, by using the higher resolution portion for interpolation,increased accuracy may be acquired in areas around the higher resolutionportion thereby increasing the accuracy of interpolation near the higherresolution portion, thereby increasing the accuracy, or overall quality,of the compressed color table (105).

FIG. 7 is a diagram of a printer cartridge (103) with a memory device(204) containing a pointer (714) to a compressed multi-dimensional colortable (105), according to one example of the principles describedherein. As described above, in some examples the color table (105) isindependent of the memory device (204). For example, the color table(105) may be located remotely from the printer cartridge (103) and maybe accessed remotely; such as via an internet connection. In thisexample, the compressed multi-dimensional color table (105) may beaccessed by a pointer (714) on the memory device (204) located on theprinter cartridge (103). An example of such a remote access is given asfollows.

In this example, the printer cartridge (103) with the correspondingmemory device (204) is installed in an output device (FIG. 1, 102) suchas a printer. A pointer (714) such as a unique identifier is read fromthe memory device (204), which uniquely identifies the color table (105)as it is stored remotely. The output device (FIG. 1, 102) or acontroller on the output device (FIG. 1, 102) looks up the color tables(105) associated with the unique identifier and transmits the colortables (105) to the output device (FIG. 1; 102) where they areauthenticated, via a digital signature for example, then stored indynamic memory or in non-volatile memory associated with the outputdevice (FIG. 1, 102) or printer cartridge (FIG. 1, 103) and associatedmemory device (204). A number of the operations described above may beperformed by the output device (FIG. 1, 102), an associated controlleror a remote service provider such as an internet service. Additionaloperations may occur such as authenticating the printer cartridge andauthenticating the printer to the remote service and authenticating thecompressed color tables to the printer.

Certain examples of the present disclosure are directed to a printercartridge (FIG. 1, 103) and a memory device (FIG. 2, 204) that includecompressed multi-dimensional color tables (FIG. 1, 105) that provide anumber of advantages not previously offered including (1) storing colortransformation information using little memory storage space on aprinter cartridge (FIG. 1, 103); (2) maintaining color transformationintegrity for easily distinguishable color transformations; (3) offeringimproved ink types that didn't exist at the time the original productwas manufactured; (4) correcting color tables in printers after start ofmanufacturing of an output device (FIG. 1, 102); (5) correcting colortables for changes in media; (6) supporting media types that didn'texist at the time an output device (FIG. 1, 102) was manufactured; (7)introducing output media with different color characteristics withoutrequiring the customer to replace all supplies to correct for errors;and (8) introducing improved color tables for a single color withoutrequiring the customer to replace all supplies to correct for errors.However, it is contemplated that the devices and methods disclosedherein may prove useful in addressing other deficiencies in a number oftechnical areas. Therefore the systems and devices disclosed hereinshould not be construed as addressing just the particular elements ordeficiencies discussed herein.

The preceding description has been presented to illustrate and describeexamples of the principles described. This description is not intendedto be exhaustive or to limit these principles to any precise formdisclosed. Many modifications and variations are possible in light ofthe above teaching.

What is claimed is:
 1. A memory device comprising: a circuit to output anumber of compressed multi-dimensional color tables to a printer toconvert a digital input color model into an output color model forphysical printing; and the number of compressed multi-dimensional colortables, wherein each compressed multi-dimensional color table comprises:at least one low dimensional portion having a number of dimensions thatis less than the number of dimensions of the compressedmulti-dimensional color table, the at least one low dimensional portionincluding color transformation information at a first resolution; and anumber of remaining portions, which are those portions which are notdefined by the at least one low dimensional portion, the remainingportions including color transformation information at a secondresolution; wherein: the at least one low dimensional portion and thenumber of remaining portions are to be interpolated to generate a highresolution uncompressed multi-dimensional color table, the highresolution being at least as great as the first resolution; the at leastone low dimensional portion is the same as a low dimensional portion ofanother memory device; and the first resolution is greater than thesecond resolution.
 2. The memory device of claim 1, wherein eachcompressed multi-dimensional color table corresponds to a particularmedia type.
 3. The memory device of claim 1, wherein the number ofcompressed multi-dimensional color tables correspond to an ink color ina cartridge in which the memory device is disposed.
 4. The memory deviceof claim 1, wherein the at least one low dimensional portion storesinformation near-neutral colors.
 5. The memory device of claim 1,wherein the at least one low dimensional portion includes a neutralaxis.
 6. The memory device of claim 1, wherein the compressedmulti-dimensional color tables correspond to a particular media color.7. The memory device of claim 1, wherein the compressedmulti-dimensional color tables correspond to a particular outputquality.
 8. The memory device of claim 1, wherein the compressedmulti-dimensional color tables correspond to a particular input device.9. The memory device of claim 1, wherein the at least one lowdimensional portion comprises multiple low dimensional portions.
 10. Thememory device of claim 9, wherein the multiple low dimensional portionscomprise one-dimensional axes.
 11. The memory device of claim 9, whereinthe multiple low dimensional portions comprise transitions from primarycolors to secondary colors.
 12. The memory device of claim 9, whereinthe at least one low dimensional portion comprises 17 points along itslength.
 13. A cartridge set comprising multiple printer cartridges, eachcartridge comprising: a memory device including a circuit to output anumber of compressed multi-dimensional color tables to a printer toconvert a digital input color model into an output color model forphysical printing; an interface to transmit the number of compressedmulti-dimensional color tables to the printer; and the number ofcompressed multi-dimensional color tables, wherein each compressedmulti-dimensional color table comprises: at least one shared lowdimensional portion having a number of dimensions that is less than thenumber of dimensions of the compressed multi-dimensional color table,the at least one shared low dimensional portion including colortransformation information at a first resolution, wherein the at leastone shared low dimensional portion is shared by multiple compressedmulti-dimensional color tables associated with the same color; and anumber of remaining portions, which are those portions which are notdefined by the at least one shared low dimensional portion, theremaining portions including color transformation information at asecond resolution, wherein the number of remaining portions aredifferent than remaining portions of different compressedmulti-dimensional color tables; wherein: the at least one shared lowdimensional portion and the number of remaining portions are to beinterpolated to generate a high resolution uncompressedmulti-dimensional color table, the high resolution being at least asgreat as the first resolution; the first resolution is greater than thesecond resolution.
 14. The cartridge set of claim 13, wherein themultiple printer cartridges comprise: a black ink cartridge; and a cyan,magenta, and yellow ink cartridge.
 15. The cartridge set of claim 13,wherein the multiple printer cartridges comprise: a black ink cartridge;a cyan ink cartridge; a magenta ink cartridge; and a yellow inkcartridge.
 16. The cartridge set of claim 13, further comprising acontroller to control distribution of output media.
 17. A memory devicecomprising: a circuit to output a number of compressed multi-dimensionalcolor tables to a printer to convert a digital input color model into anoutput color model for physical printing; and the number of compressedmulti-dimensional color tables, wherein each compressedmulti-dimensional color table comprises: a first number of shared nodesalong a low dimensional portion having a number of dimensions that isless than the number of dimensions of the compressed multi-dimensionalcolor table, the first number of nodes including color transformationinformation at a first resolution, wherein the first number of sharednodes are shared by multiple compressed multi-dimensional color tablesassociated with the same color; a second number of nodes along a numberof remaining portions, which are those portions which are not defined bythe at least one low dimensional portion, the second number of nodesincluding color transformation information at a second resolution; and athird number of nodes along an intermediate portion of eachmulti-dimensional color table including color transformation informationat a third resolution, in which the remaining portions comprise thoseportions not comprising the low dimensional portion and the intermediateportion; wherein: the first number of shared nodes, the second number ofnodes, and the third number of nodes are to be interpolated to generatea high resolution uncompressed multi-dimensional color table, the highresolution being at least as great as the first resolution; the firstresolution is greater than the second resolution.
 18. The memory deviceof claim 17, wherein the compressed multi-dimensional color tablescorrespond to a particular media color.
 19. The memory device of claim17, wherein the compressed multi-dimensional color tables correspond toa particular output quality.
 20. The memory device of claim 17, whereinthe compressed multi-dimensional color tables correspond to a particularinput device.